Wortels van vierkantsvergelijkingen oplossen, yay

gistfile1.scm

(define (discriminant a b c)
  (- (expt b 2) (* 4 a c)))

(define (wortel a b c)
  (if (> (discriminant a b c) 0)
      (list (/ (- (- b) (sqrt (discriminant a b c))) (* 2 a)) (/ (+ (- b) (sqrt (discriminant a b c))) (* 2 a)))
      (if (= (discriminant a b c) 0)
          (/ (- (- b)) (* 2 a)) 
          "Imagine a solution"))) 
            
(define (vierkantsvgl a b c)
      (wortel a b c))

(vierkantsvgl 1 1 1)
(vierkantsvgl 1 2 1)
(vierkantsvgl 1 5 1)